One of the most common skin problems with infants relates to diaper rash, also known as diaper dermatitis. One study conducted with infants less than two years of age concluded that almost two-thirds of all infants suffer from diaper rash of some degree. Approximately 10% of all infants can have their diaper rash classified as being moderate, with another 5% of the infants having diaper rash which could be classified as severe.
The primary contributors to the development of diaper rash have long been thought to be infant urine and feces. For example, infants under two months of age can urinate up to 20 times per day. Thereafter, infants can urinate up to 8 times a day. In addition, infant defecation typically occurs several times a day.
It had been theorized that the breakdown of the urine to yield ammonia primarily contributed to the formation of diaper rash by increasing the alkalinity of the skin. However, more recent studies have concluded that the primary contributor to the development of diaper rash is feces. As opposed to the alkaline pH associated with urine, feces typically exhibits an acidic pH due to bile. In fact, studies have shown that diaper rash is more prominent in the presence of feces than in the presence of urine, thereby providing a plausible explanation for the problems with diaper rash associated with infants who have diarrhea or frequent stools.
Diaper rash may predispose an infant to irritation and infection. The two most common types of infection are those associated with yeast, and bacteria. The most common yeast infection is caused by Candida albicans. Meanwhile, the most common bacterial infection is caused by Staphylococcus aureus.
Treatment for diaper rash involves removing the source of irritation, reducing the immediate skin reaction, relieving the discomfort and preventing secondary infection and other complications. Frequent diaper changes and keeping the area as dry and clean as possible normally prove helpful. However, merely keeping the area clean and dry does not protect the irritated skin from the chemical irritation associated with the by-products of infant urine and feces.
In response to the problems associated with diaper rash, a number of products have been made available. The principle function of these products has been to act as a protectant, such that any affected area is protected against further direct contact with urine or feces. The most widely used protective ingredient has been zinc oxide. While many preparations contain zinc oxide in concentrations of approximately 10% by weight, some of the more popular brands have zinc oxide concentrations of approximately 40% by weight. Unless otherwise stated, the percentage concentrations of ingredients is understood to refer to present by weight. Typically the zinc oxide is formulated with an oily substance such as petrolatum. Consequently, although such a diaper rash compound provides an effective protective layer, it is greasy, messy to apply, and not easily removed from the hands or the baby's bottom. Although removal can be affected with mineral oil, having to wash one's hands with mineral oil is inconvenient. Additionally, zinc oxide products have a distinctive smell due to their oil base, with this smell being offensive to some users of the product.
Most of the diaper rash products currently available are in the form of an ointment or a water-in-oil emulsion. The high viscosity associated with these products keeps the diaper rash product from being washed away by urine or feces. In many cases, the high viscosity is the result of the inclusion of zinc oxide. Thus, the typical anhydrous, hydrophobic ointment prevents urine or feces from coming into direct contact with the skin by their being repelled from the ointment surface. As such, the product acts as a barrier, inhibiting any penetration into the diaper rash product by any liquid.
An example of a diaper rash product is British Patent No. 1,357,731. That patent discloses a unique powder composition, which can be incorporated into a hydrophobic ointment. A buffer system is provided to buffer the composition at a pH of from 5.5 to 7.5, and preferably from 6 to 7. That patent discloses that a citric acid/sodium citrate buffering system does not have superior buffering capacity when compared with other buffering systems. This patent further discloses that "succinic acid/sodium succinate has 30% more buffering capacity than a citric acid/sodium citrate" buffer system. Thus this patent differs from the instant Invention in that it claims use of a powder formulation having buffering capacity in the alkaline range of pH 5.5 to 7.5, and teaches away from the use of citric acid buffering system in view of the aforenoted comments related to the preferred use of a succinic acid buffer.
Another example of the prior art is U.S. Pat. No. 4,556,560 issued on Dec. 3, 1985 to Buckingham. This patent discloses and claims use of lipase inhibiting agents, such as the water soluble metallic salts including zinc chloride, in the treatment of diaper rash. This patent purports to treat diaper rash by inhibiting the deleterious effects of the enzyme lipase action on the skin, said inhibition being achieved by incorporating a inhibitory agent of said lipase action into a barrier like carrier, said carrier having the characteristics of being relatively hydrophobic in nature thereby forming an effective barrier to the skin against urine and feces. The instant Invention does not disclose nor claim use of lipase inhibitory agents. The instant Invention is further distinguished from the Buckingham patent in that the present invention specifically claims use of a buffering sysytem to neutralize acidic conditions. Buckingham neither teaches nor claims any buffering system. Further the instant Invention is see apart from the Buckingham patent in the nature of the carrier material employed in the formation of the so-called skin barrier. In the case of Buckingham, specifically disclosed are water-in-oil types of emulsions. In contrast to Buckingham, the instant Invention specifically discloses and claims use of oil-in-water type emulsions in the formation of the barrier material.
Yet another example of the prior art is U.S. Pat. No. 4,996,238 issued on Feb. 26, 1991 to Matravers. This patent discloses and claims a skin protective composition exhibiting enhanced water repellency and skin conditioning effects and contains aliphatic waxes and hydrophobic silicones. Matravers' specificially discloses and claims the use of an admixture consisting of a fatty acid admixed with one or more hydrophobic silicones. This composition is devoid of water and further no buffering system is claimed. In contrast, the instant Invention claims a water-based liquid product which contains a buffering system effective in acidic conditions.
Another example of the prior art is U.S. Pat. No. 4,904,524 issued on Feb. 27, 1990 to Yoh. This patent discloses and claims the encapsulation and microbead formation and use thereof of the active silicon agent (Dimethicone) in the preparation of cloth wipes in the treatment of diaper rash. This patent specifically discloses the need for an elevated concentration of encapsulated beads containing the active agent at the surface of the wipe. The stability, presence and delivery of the active agent within the wipe is directly linked to, and dependent on the process used to form and adhere the encapsulated beads to the paper wipe. In contrast, the instant Invention claims a water-based liquid product which contains a buffering system effective in acidic conditions. Further, the instant Invention does not require, teach nor claim encapsulation of Dimethicone, one of the ingredients in the claimed composition.
Other studies, such as one published in The Practitioner, Vol 210:824-828 (1973), discuss a boric acid/borax buffer system for use as a diaper rash product. However, studies conducted during the 1970's brought about concerns of boron toxicity such that products containing boric acid had to be reformulated thereby eliminating boric acid as an ingredient.
Still another approach to products containing anhydrous, hydrophobic zinc oxide was the incorporation into such products of alkoxylated ether/esters Such as polypropyleneglycol myristyl ether propionate. Although this approach rendered the diaper rash products less greasy, it did not completely resolve the problem associated with the zinc oxide content.
It is thus apparent that a need exists for an improved diaper rash product which provides a safe system, which is easy to apply as well as easy to remove by simple cleaning agents such as soap and water.